True Learn Main points 1 Flashcards
A resident is preparing to transport an intubated patient from the OR to the ICU and is worried about being trapped in a broken elevator and running out of oxygen. The pressure gauge on the size E compressed oxygen cylinder reads 1500 psi. How long could oxygen be delivered from this cylinder at a rate of 4 Liters/minute assuming oxygen flow will stop at 0 psi?
A quick way to approximate the time remaining in a size E compressed oxygen tank is the “rule of 3”. Divide the new pressure by 3 and this gives a rough estimate of the volume remaining in the tank (since the approximate ratio of oxygen E-cylinder pressure to volume is 3 : 1 (2000 : 625)). Then divide volume remaining by the flow rate. For example, if there is 1500 psig in the tank at a flow rate of 4L/min, time remaining would be (1500/3)/4 = 125 minutes.”
TrueLearn Insight : E-cylinders of nitrous oxide are filled to 90% to 95% of their capacity with liquid nitrous oxide. Above the liquid in the tank is nitrous oxide vapor, that is, gaseous nitrous oxide. Unlike oxygen, the content of a tank of nitrous oxide cannot be determined from the pressure gauge as long as it reads 745 psi. The only way it can be determined is by weighing the tank. However, when all the liquid nitrous oxide in the tank has been used up and the tank contains only gaseous nitrous oxide, then the pressure will decrease proportionally to the remaining amount. It should be noted that once this happens, approximately 75% of the tank is empty.
During oscillometric non-invasive blood pressure measurement, how is the mean arterial pressure (MAP) determined?
The point of maximal amplitude of oscillations corresponds to the mean arterial pressure (MAP). The values of systolic and diastolic pressures are determined using formulas that detect the rate of change in the oscillations.
Which of the following design features is MOST LIKELY to be found in modern endotracheal tubes?
Features of the modern endotracheal tube include a high-volume/ low-pressure cuff, PVC construction with a longitudinal radio-opaque line, a beveled distal tip with Murphy eye, 15 mm external diameter circuit adapters, and the incorporation of ultra-thin polyurethane cuffs to decrease the incidence of micro-aspiration.
TrueLearn Insight : Inflation of an ETT cuff with 50/50 N2O/Air mixture prior to a planned anesthetic that will utilize N2O has been shown to mitigate the concern for cuff over-distension and possible tracheal injury in the setting of N2O use.
A nitrous oxide E-cylinder reads 745 psig. Which of the following BEST estimates the liters of nitrous oxide available for use?
The volume of nitrous oxide remaining in an E-cylinder with a full pressure reading can only accurately be determined by comparing the current weight of the cylinder to the tare weight. The gauge pressure will continue to read 745 psig (“full”) until approximately 16% or 253 liters of the nitrous oxide remains.
Which of the following factors related to the carbon dioxide absorbent would MOST contribute to carbon monoxide toxicity?
There are multiple factors that contribute to carbon monoxide production, including:
1) Presence of strong bases in the CO2 absorbent (TOP FACTOR)
2) Volatile agent used (Desflurane > Enflurane > Isoflurane»_space; Sevoflurane = Halothane)
3) Desiccation of absorbent
4) Low fresh gas flows
5) High inspired concentration of volatile agent
6) Increased absorbent temperature
A 40-year-old 90 kg male is undergoing open cholecystectomy under general anesthesia. You suspect a leak in the circle system. Which of the following is LEAST likely true?
Ascending bellows have the advantage of providing a visual sign of system leak versus a descending bellows which can continue to fill with room air and would fail to detect a system leak.
Which of the following nail polish colors is LEAST likely to interfere with pulse oximeters?
Blue, green, and to a lesser extent, black nail polish cause falsely low oxygen saturations to be displayed by standard two-wave pulse oximeters by interfering with the differential absorption of 660 and 940 nm light.
Red nail polish does not significantly decrease oxygen saturation readings from standard pulse oximeters.
Which of the following could result in a failure of the bellows to rise in an ascending (standing) bellows ventilator during mechanical ventilation?
In a typical ascending (standing) bellows ventilator, the bellows rise during patient exhalation. The bellows can act as an indicator of a leak or a disconnection of the circuit from the patient because the patient’s exhaled gases will exit the system and will not be able to fill the bellows, leaving them collapsed.
A patient’s blood pressure is 130/75 measured by a radial arterial catheter. If the operating room table is lowered 15 cm relative to the transducer, the patient’s blood pressure will display closest to which of the following?
Raising or lowering a pressure transducer relative to the patient (or the patient relative to the transducer) will alter the pressure reading. A 10 cm change in height will alter the pressure reading by 7.5 mm Hg. Raising the transducer (lowering the patient) lowers the pressure reading. Lowering the transducer (raising the patient) increases the pressure reading.
Elective subglottic jet ventilation for laryngeal papilloma resection is initiated in an otherwise healthy patient. Which of the following is the MOST likely complication associated with this airway management technique?
One of the most common complications of transtracheal or subglottic jet ventilation is hypercarbia. Other important complications include impaired respiratory ciliary function, hypoxia, and loss of the airway. Rarely, subcutaneous emphysema, pneumothorax, and pneumomediastinum can result from barotrauma while necrotizing tracheobronchitis can occur from prolonged use.
Which of the following statements is FALSE regarding the negative pressure leak test?
The three most important preoperative anesthesia machine checks are oxygen analyzer calibration, low-pressure circuit leak test, and the circle system test.
A desflurane vaporizer calibrated for use at sea level is being used at 18,000 feet (barometric pressure of 380 mmHg). What is the MAC if the concentration dial is set to 6%?
A desflurane vaporizer is a dual-gas blender that heats the gas to a pressure of 2 atm absolute to maintain a constant concentration of vapor output, not a constant partial pressure.
TrueLearn Insight : Anesthetic delivered through a variable bypass vaporizer (e.g. sevoflurane, isoflurane, enflurane) will deliver approximately the same MAC at higher or lower elevations. Gas delivered through a dual-gas blender, such as used with desflurane, will deliver anesthetic directly proportional to the atmospheric pressure change. Another way of saying this is gas delivered will be inversely proportional to altitude.
Which of the following is true regarding the precision and accuracy of a monitor?
A monitor can be precise, accurate, both, or neither. Accuracy is how close a value is to the true value. Precision is how repeatable the measurements are. In other words, accuracy is defined by the mean of the measurement, while precision is defined by the standard error of the measurement. An imprecise monitor cannot be improved by re-calibration.
An anesthesia machine circle system is shown below, but has a major flaw due to incorrect placement of which of the following?
The fresh gas inlet should not be positioned between the patient and the inspiratory or expiratory valves in a traditional circle system.
A mountaineer ascends to a summit where the barometric pressure is 0.5 atmosphere. Which of the following is the partial pressure of oxygen at this elevation?
0.105 atms
